Particle size analyzer based on the laser diffraction method

Scattered light obtained by irradiating parallel laser beam to particles to be measured is condensed by a condenser lens in a wide angle area from 0° to over 40°, and an intensity distribution of the light is spatially continuously measured by an optical sensor positioned at a focal point of the condenser lens. Before a particle size distribution is calculated from the measured light intensity distribution, measuring error of the scattered light intensity distribution caused by an aberration by the condenser lens and an attenuation on the optical path is corrected by comparing with data obtained through a ray tracing in advance. Thus, the scattered light in a wider angle area are spatially continuously measured to thereby obtain a light intensity distribution with a high resolution in a submicron area.